Bump testContainersVersion from 1.21.2 to 1.21.3 in /Plan (#4152)

Bumps `testContainersVersion` from 1.21.2 to 1.21.3.

Updates `org.testcontainers:testcontainers` from 1.21.2 to 1.21.3
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.21.2...1.21.3)

Updates `org.testcontainers:junit-jupiter` from 1.21.2 to 1.21.3
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.21.2...1.21.3)

Updates `org.testcontainers:nginx` from 1.21.2 to 1.21.3
- [Release notes](https://github.com/testcontainers/testcontainers-java/releases)
- [Changelog](https://github.com/testcontainers/testcontainers-java/blob/main/CHANGELOG.md)
- [Commits](testcontainers/testcontainers-java@1.21.2...1.21.3)

---
updated-dependencies:
- dependency-name: org.testcontainers:testcontainers
  dependency-version: 1.21.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.testcontainers:junit-jupiter
  dependency-version: 1.21.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.testcontainers:nginx
  dependency-version: 1.21.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Plan/build.gradle

@@ -93,7 +93,7 @@ subprojects {
         junitVersion = "5.13.3"
         mockitoVersion = "5.18.0"
         seleniumVersion = "4.34.0"
-        testContainersVersion = "1.21.2"
+        testContainersVersion = "1.21.3"
         awaitilityVersion = "4.3.0"
         swaggerVersion = "2.2.34"
         guavaVersion = "33.4.8-jre"